1. Field of the Invention
The invention relates to a gas supply system. More particularly, the invention relates to a gas supply system that includes a plurality of gas containers and that is capable of avoiding an incorrect control resulting from a delay of the time of the rising of supply pressure of gas which results from a difference in pressure between gas containers.
2. Description of Related Art
In response to growing awareness about energy saving and global environment protection in these days, electric vehicles equipped with electric motors as a motive power source, for example, are coming into widespread use. Along with this trend, research and development are being vigorously Pursued on electric power sources for electric motors used as motive power sources of such electric vehicles, for example, a fuel cell that generates electricity through an electrochemical reaction of hydrogen with oxygen from the air. The hydrogen for use in the fuel cell is often in the gas state since hydrogen is easier to handle in the gas state than in the liquid state. Therefore, means often used to store hydrogen gas is, for example, a high-pressure container such as a tank or the like. Furthermore, hydrogen gas motor vehicles equipped with an internal combustion engine that burns hydrogen gas instead of a fossil fuel, for example, gasoline or the like, are drawing attention in view of environmental issues. The hydrogen gas motor vehicles are also generally equipped with a high-pressure container for storing hydrogen for substantially the same reason as mentioned above.
A material used for the aforementioned high-pressure container can be a metal, for example, iron or the like, from the viewpoint of strength and air tightness. However, from the viewpoint of weight reduction, a material obtained by reinforcing a base material of a plastic, for example, polyethylene or the like, with a reinforcing material, for example, carbon fiber or the like, for improved pressure resistance is also used. Furthermore, when the hydrogen gas stored in, for example, a high-pressure container decreases in amount as it is consumed, the high-pressure container can be re-charged from a hydrogen gas supply source that is installed at a hydrogen gas station or the like. Incidentally, the storage means for hydrogen gas can also be constructed of a plurality of high-pressure containers.
In a gas supply system which supplies a gas from a high-reassure container to a mechanism that functions by using the gas (hereinafter, sometimes referred to as “gas usage mechanism”), for example, a fuel cell, an internal combustion engine, etc., and which is equipped with a plurality of high-pressure containers, if the pressures of the gas stored in the high-pressure containers (internal pressures of the high-pressure containers) vary between a high-pressure containers, the gas flows from the high-pressure container that has relatively high internal pressure to a high-pressure container that has relatively low internal pressure, giving rise to possibility of occurrence of a phenomenon, such as a change in temperature resulting from adiabatic irreversible expansion of the gas in the high-pressure container that has relatively low internal pressure (e.g., the Joule-Thomson effect in hydrogen gas, or the like), or a delay of the rising of the pressure of the gas in the supply channel when the gas starts to be supplied to the gas usage mechanism, etc.
Therefore, in this technical field, with, regard to the aforementioned phenomenon of a change in temperature, there is a technology, for example, in which a gas supply system equipped with a plurality of high-pressure containers is provided with reverse flow prevention means, such as a check valve or the like, for preventing a gas from flowing from a gas supply channel side to the high-pressure containers, in order to prevent an event in which the gas flows from a high-pressure container that has relatively high internal pressure to a high-pressure container that has relatively low internal pressure, and heat production due to adiabatic compression of the gas (and, in the case of hydrogen gas or the like, heat production due to the Joule-Thomson effect associated with adiabatic irreversible expansion of the gas) occurs resulting in rapid rise of the temperature in the high-pressure container that has relatively low internal pressure (e.g., see Japanese Patent Application Publication No. 2002-206696 (JP 2002-206696 A)). There also exists a technology related to a gas supply system equipped with a plurality of high-pressure containers in which, in order to prevent an event in which if the high-pressure containers are charged with a gas when the remaining amounts of the gas in the high-pressure containers are not uniform (i.e., vary), heat production due to adiabatic compression of the gas associated with the charging with the gas occurs concentratedly in a high-pressure container whose remaining amount of the gas is small (whose internal pressure is low), the gas is allowed to flow between the high-pressure containers prior to the charging of the containers with the gas so as to reduce the differences between the internal pressures of the high-pressure containers (e.g., see Japanese Patent Application Publication No. 2005-226716 (JP 2005-226716 A)).
With regard to the phenomenon of delay of the rising of the pressure, however, the fact of the matter is that the latter one of the aforementioned phenomena has not drawn much attention in this technical field. That is, this technical field has not found an effective solution to the delay of the rising of the pressure in the gas supply channel which occurs when the gas starts to be supplied to a gas usage mechanism.
In the meantime, in this technical field there exists, for example, a gas supply system that is equipped with a plurality of high-pressure containers and that determines whether to continue supplying a gas to a gas usage mechanism on the basis of the pressure of the gas in a gas supply channel to the gas usage mechanism. In such a gas supply system, if the pressures of the gas stored in the high-pressure containers (internal pressure) vary among the high-pressure containers, the gas flows from a high-pressure container that has relatively high internal pressure to a high-pressure container that has relatively low internal pressure, so that the rising of the pressure in the gas supply channel when the gas starts to be supplied to the gas usage mechanism delays, as mentioned above. As a result, in the gas supply system, there arises possibility, for example, that the delay of the rising of the pressure in the gas supply channel when the gas starts to be supplied may be incorrectly recognized as resulting from insufficient amount of the gas remaining and the supply of the gas may be incorrectly stopped (and the function of the gas usage mechanism that requires supply of the gas may be incorrectly stopped).
Therefore, in this technical field there is demand for a technology in a gas supply system that supplies a gas from a plurality of gas containers to a gas usage mechanism (e.g., a fuel cell, an internal combustion engine, etc.) which makes it possible to reduce the event in which if the rising of the pressure in the gas supply channel at the time of start of supply of the gas delays due to imbalance in the internal pressure between the plurality of gas containers, it is incorrectly recognized that the remaining amount of the gas is insufficient.